When to use limited stash of Trimix on a boat trip? Early or later?

[jgttrey]

My reference to literature ("Recreational Trimix Diving") points to potential narcosis from high O2 as well and it likely demands mixes that closer to normoxic rather than EAN. I will attempt to keep the PP of O2 low (in the 1.0 atm or lower) as well as the PP of N2 below that for air at 80ft. Like the contributors have said, it will demand a mix of not 28/25 but more in the range of 23/30 or 21/35 for dives to the 110 to 130ft range.
My spreadsheet of various mixes and the PP of N2 at various depths will be updated with a column of PP for O2. Next is to model lots of simulated dives using MAC compatible software (I still need to find). Thanks for the comments.

-T

Suggest you download Multideco or the like. Set O2 as narcotic and then run your scenarios. You can also run out repetive dives.

Even if you treat O2 as narcotic, I would rethink lowering the FO2. I don't understand the logic there. It's just going to limit your bottom time for no good reason. Reduce narcotic effect by substituting helium for nitrogen, not O2.

Pick the max PO2 you are comfortable with, presumably 1.4. Figure the FO2 that gives you that PO2 at your max depth. That's your best O2%. Then figure out how much helium you need so that you get an acceptable END. That's the basic 2 step gas mix planning in your recreational tmx book.

28/25 would be my choice FWIW.

Sorry if I missed something.